Wednesday, May 11th, 2005

XMLHttpRequest tracing for Ajax debugging via GreaseMonkey

Category: Ajax, Utility

Julien Couvreur has written a GreaseMonkey user script to:

trace XMLHttpRequest calls in the javascript console. It logs the “open” and “send” calls, as well as the response status code and text.

Its purpose is to help peek into Ajax applications, to learning or troubleshooting, without having to run a network sniffer.

Here is a screenshot showing the output running on Google Suggest:

This is an early version, so some problems exist.

Posted by Dion Almaer at 11:26 am

3 rating from 6 votes


Comments feed

LiveHTTPHeaders ( is also a good option for this – more of a swiss army knife, also allows replay.

Comment by Michal Migurski — May 11, 2005

Actually, Adrian Holovaty also brought up Live HTTP Headers on my blog. But it is not that suitable for debugging AJAX: it doesn’t show the body of the response.
Also, I’m working on more AJAX-specific features (not available in Live HTTP Headers), such as edit and replay for callbacks, and possibly even setting breakpoints and editing XMLHttpRequest calls.

Comment by Julien Couvreur — May 11, 2005

There’s also httpheaders add in for internet explorer,
few other mentioned on IE blog:

Comment by M.J.Milicevic — May 12, 2005

And, of course, there’s the buzzsaw of network troubleshooting tools (and my personal favorite), ethereal.

Comment by Alex Russell — May 12, 2005

Just posted a new version, with some debugging features such as: edit&replay request, replay response callback,…
It’s at

Comment by Julien Couvreur — June 1, 2005

If you are using windows, then is damn fantastic for debugging an HTTP message flow.

I use it with Firefox by setting it up as a proxy using the SwitchProxy from

Within fiddler you can even manually edit and then resend GET/POST requests – useful!

Comment by Morris Johns — October 5, 2005

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